The present invention relates to a compound for dispersing a particulate solid in a liquid medium, its method of preparation and to compositions and millbases containing said compound and a particulate solid, including paints and inks.
WO 97/19948 discloses a dispersant which is a phosphate ester of a block copolymer ROxe2x80x94(C2H4O)m(PES)nxe2x80x94OH wherein R is C1-4-alkyl, PES is a polyester derived from a cyclic lactone such as valerolactone or xcex5-caprolactone, m is from 5 to 60, n is from 2 to 30 and where the molecular weight of RO(C2H4O)m is greater than the molecular weight of (PES)n. The dispersants are said to be particularly effective for dispersing particulate solids such as pigments in an aqueous medium.
It has now been found that dispersants exhibiting superior properties such as solubility in the liquid medium can be obtained by using more than one hydroxycarboxylic acid or lactone to make the polyester (PES)n.
According to the invention there is provided a dispersant which is a phosphate ester of a polymer which contains at least one ether group and a poly(oxyalkylenecarbonyl) chain derivable from two or more different hydroxycarboxylic acids or lactones thereof including their salts. The dispersant is hereinafter referred to as xe2x80x9cEther dispersantxe2x80x9d. Preferably, the poly(oxyalkylenecarbonyl) chain is derivable from two different hydroxy carboxylic acids or lactones thereof. The molecular weight of the polymer can vary between wide limits depending whether the dispersant is to be used for dispersing a particulate solid in a polar liquid medium including water or whether it is for use in a substantially non-polar liquid medium. The molecular weight of the polymer is typically from 200 to 10,000, preferably from 300 to 5,000 and especially. from 400 to 2,000.
According to a preferred aspect of the invention, the dispersant is a phosphate ester of a copolymer of formula 1
RO"Brketopenst"(COxe2x80x94Axe2x80x94O)n(COxe2x80x94Bxe2x80x94O)m"Brketclosest"Hxe2x80x83xe2x80x83(1)
including salts thereof wherein
R is a polymerisation terminating group containing at least one ether link;.
A and B are each, independently, different alkenylene groups or C1-17-alkylene groups optionally substituted by alkyl;
n and m are integers; and
n+m is from 2 to 200.
The copolymer of formula 1 may be a block or random polymer.
In the dispersant of formula 1, [(COxe2x80x94Axe2x80x94O)n(COxe2x80x94Bxe2x80x94O)m] represents a polyoxyalkylenecarbonyl chain and the group RO may be attached to either of the oxyalkylenecarbonyl groups containing A and B. It is referred to hereinafter as a pplyoxyakylenecarbonyl chain or POAC chain. The copolymer of formula 1 containing the polymerisation terminating group is referred to hereinafter as a TPOAC alcohol.
Where A and/or B is alkenylene it is preferably C2-17-alkenylene and especially C15-17-alkenylene.
When the dispersant is for use in a non-polar medium, it is preferred that at least one of A and B is C8-17-alkylene and when the dispersant is for use in a polar liquid medium, including water, it is preferred that one, or more preferably both, A and B are C1-6-alkylene and especially C4-6-alkylene optionally substituted by alkyl.
The alkyl substituent in A and B may be linear or branched and is preferably C1-8-alkyl, more preferably C1-6-alkyl and especially C1-4-alkyl.
It is particularly preferred that the molecular weight of the ether moiety RO is greater than that of the POAC chain.
The polymerisation terminating group R containing at least one ether group is preferably a residue of a mono-hydroxy glycol or a mono-hydroxy polyalkyleneglycol. Preferred glycols or polyalkyleneglycols are those derivable from C2-4alkyleneoxide, especially ethyleneoxide or propyleneoxide, including mixtures thereof. When the dispersant is for use in a polar liquid, including water, the glycol or polyalkyleneglycol is preferably derivable from ethylene oxide and when the dispersant is for use in a non-polar liquid medium, the glycol or polyalkyleneglycol is preferably derivable from propyleneoxide. When the dispersant is for use in a polar liquid medium, including water, it is particularly preferred that the glycol or polyalkyleneglycol is derivable from ethylene oxide and that both A and B are different C1-6-alkylene groups.
Examples of hydroxycarboxylic acids are 12-hydroxystearic, ricinoleic, 12-hydroxydodecanoic, 5-hydroxydodecanoic, 5-hydroxydecanoic, 4-hydroxydecanoic, glycolic, lactic, 6-hydroxyhexanoic and 5-hydroxypentanoic acids.
Examples of lactones are propiolactone, butyrolactone, valerolactone (especially xcex4-valerolactone) and optionally alkyl-substituted xcex5-caprolactone. The alkyl substituent in xcex5-caprolactone may be linear or branched and is preferably C1-8-alkyl, more preferably C1-6-alkyl and especially C1-4-alkyl. Examples of such groups are methyl and tertiary butyl.
The alkyl-substituted xcex5-caprolactones are obtainable by oxidation of alkyl-substituted cyclohexanone and consequently many are mixtures of alkyl-substituted xcex5-caprolactone. Thus, the oxidation of 2-methyl cyclohexanone often results in a mixture of 7-methyl (95%) and 3-methyl (5%) xcex5-caprolactone. However, the oxidation of 4-alkylcyclohexanone results only in the 5-alkyl xcex5-caprolactone. Other examples of alkyl-substituted xcex5-caprolactone are 6-methyl; 4-methyl; 5-methyl; 5-tertiary butyl; 4,6,6-trimethyl and 4,4,6-trimethyl derivatives. 7-methyl xcex5-caprolactone is the preferred alkyl-substituted xcex5-caprolactone.
The polymerisation terminating group R is preferably derived from a hydroxy compound Txe2x80x94OH which is attached to the glycol or polyalkyleneglycol by an ether linkage wherein T is C1-35-hydrocarbyl which is optionally substituted by halogen, tertiary amino, hydroxy, C1-6-alkoxy, amine, ester or urethane groups.
When T contains amide, ester or urethane groups it preferably contains two such groups and the group R is preferably a diester, diamide or di-urethane containing at least one ether link. Groups represented by R which contain either amide, ester or urethane groups are conveniently prepared by reacting two fragments of T which contain a hydroxy or amino group with, for example, a dibasic acid or anhydride thereof or a di-isocyanate.
Examples of dibasic acids or anhydrides are terephthalic, phthalic anhydride, adipic acid, maleic acid and maleic anhydride.
Examples of di-isocyanates are toluene di-isocyanate and isophorone di-isocyanate.
The group T may be aromatic, hetrocyclic, alicyclic or aliphatic which may be linear or branched, saturated or unsaturated. It is preferred that T contains not greater than 20 carbon atoms and particularly not greater than 10 carbon atoms. It is especially preferred that T is C1-6-alkyl such as methyl.
Other examples of the group T are C2H5xe2x80x94, CH3(CH2)9xe2x80x94, CH3(CH2)11xe2x80x94, CH3(CH2)15xe2x80x94, CH3(CH2)17xe2x80x94, CH3(CH2)29xe2x80x94, CH3(CH2)7CHxe2x95x90CH(CH2)7xe2x80x94, CH3OCH2xe2x80x94, CH3(CH2)4CHxe2x95x90CHCH2CHxe2x95x90CH(CH2)7xe2x80x94 the residue of abietyl alcohol, i.e. abietyl alcohol without the OH group, nonylphenol.
As noted hereinbefore, it is particularly preferred that T is C1-6-alkyl and also that R is derivable from ethylene oxide since such dispersants have been found particularly effective in dispersing particulate solids in a polar liquid medium, including water.
Examples of R containing at least one ether link are the residue of tripropyleneglycol monomethylether, dipropyleneglycol monomethylether, triethyleneglycol monomethylether, methoxypropyleneglycols and methoxyethyleneglycols having a molecular weight between 250 and 750, ethoxylated C9-11-fatty alcohol with a molecular weight of 270 and ethoxylated nonylphenol having a molecular weight of 360.
The dispersant of Formula 1 is obtainable by polymerising two different hydroxycarboxylic acids or lactones thereof in the presence of a monohydric alcohol Rxe2x80x94OH to form a TPOAC alcohol having a terminal hydroxy group i.e. a POAC chain having a terminal hydroxy group and a polymerisation terminal group. The TPOAC alcohol is subsequently reacted with a phosphating agent, especially P2O5 and polyphosphoric acid.
The TPOAC alcohol may be prepared by reacting the hydroxy carboxylic acids or lactones thereof together and then reacting the compound so formed containing the POAC chain with a polymerisation terminating compound. However, it is preferred to form the TPOAC alcohol directly by reacting the hydroxy carboxylic acids, or lactones thereof, in the presence of a polymerisation terminating compound. The reaction is preferably carried out in an inert atmosphere and optionally in the presence of an inert solvent and esterification catalyst. The reaction is typically carried out between 150 and 180xc2x0 C. It is also preferred to carry out the reaction in the absence of an inert solvent.
Examples of suitable catalysts are tetra-alkyl titanate, for, example, tetrabutyltitanate, zinc salt of an organic acid such as zinc acetate, tin salts of organic acids such as dibutyl tin dilaurate, zirconium salt of an aliphatic alcohol such as zirconium isopropoxide, toluenesulphonic acid or a strong organic acid such as haloacetic acid and particularly trifluoroacetic acid.
The dispersant which is a phosphate ester of Formula 1 is obtainable by reacting a TPOAC alcohol with a phosphating agent wherein the ratio of the alcohol to each phosphorus atom of the phosphating agent is from 3:1 to 1:1 and especially from 2:1 to 1:1. It is especially preferred that the ratio of each TPOAC alcohol to each phosphorus atom of the phosphating agent is less than 2, for example, about 1.5:1 when the dispersant is a mixture of mono- and di-phosphate esters.
The reaction between the TPOAC alcohol and phosphating agent is preferably carried out in an inert atmosphere such as nitrogen, under anhydrous conditions. The reaction may be carried out in an inert solvent but it is more convenient to react the TPOAC alcohol with the phosphating agent in the absence of a solvent. The reaction temperature is preferably above 60 and especially above 80xc2x0 C. In order to avoid charring the dispersant, the temperature is preferably less than 120 and especially less than 100xc2x0 C.
As a less preferred variant, the dispersant of Formula 1 may also be prepared by reacting a monohydric, alcohol with a preformed POAC acid and subsequently reacting the TPOAC alcohol with a phosphating reagent.
The dispersants may also contain additional ester, amide or amine salt groups formed by reacting the dispersant with an alcohol or alkanolamine.
The dispersants may be in the form of a free acid or it may form a salt with an alkali metal, ammonia, an amine, alkanolamine or quaternary ammonium salt depending whether the dispersant is to be used to disperse a particulate solid in a polar medium, including water, or in a non-polar medium. When the medium is a polar medium or water, the dispersant is preferably in the form of its free acid or in the form of its alkali metal salt and when the medium is a non-polar medium the dispersant is preferably in the form of a salt with an amine. Examples of suitable amines are n-butylamine, diethanolamine and dimethylaminopropylamine.
The TPOAC alcohols used in the preparation of the dispersants are novel.
Thus, according to the invention there is provided a TPOAC alcohol of formula RO[(COxe2x80x94Axe2x80x94O)n(COxe2x80x94Bxe2x80x94O)m]H wherein R, A, B, n and m are as defined hereinbefore.
As noted hereinbefore, the dispersants are particularly useful for dispersing a particulate solid in a liquid medium.
According to a further aspect of the invention there is provided a composition comprising a particulate solid and an Ether Dispersant.
According to a still further aspect of the invention there is provided a dispersion comprising an Ether Dispersant, a particulate solid and a liquid medium.
The solid present in the dispersion may be any inorganic or organic solid material which is substantially insoluble in the liquid medium at the temperature concerned and which it is desired to stabilise in a finely divided form therein.
Examples of suitable solids are pigments for solvent inks; pigments, extenders, fibres and fillers for paints and plastics materials; dyes, especially disperse dyes; optical brightening agents and textile auxiliaries for solvent dyebaths, inks and other solvent application systems; solids for oil-based and invert-emulsion drilling muds; dirt and solid particles in dry cleaning fluids; particulate ceramic materials; magnetic materials and magnetic recording media, and biocides, agrochemicals and pharmaceuticals which are applied as dispersions in organic media.
Examples of suitable plastics materials are synthetic resins such as those used as sheet moulding compounds and bulk, moulding compounds which comprise unsaturated polyester resins containing reinforcing fibres and fillers.
A preferred solid is a pigment from any of the recognised classes of pigments described, for example, in the Third Edition of the Colour Index (1971). and subsequent revisions of, and supplements thereto, under the chapter headed xe2x80x9cPigmentsxe2x80x9d. Examples of inorganic pigments are titanium dioxide, zinc oxide, Prussian blue, cadmium sulphide, iron oxides, vermilion, ultramarine and the chrome pigments, including chromates, molybdates and mixed chromates and sulphates of lead, zinc, barium, calcium and mixtures and modifications thereof which are commercially available as greenish-yellow to red pigments under the names primrose, lemon, middle, orange, scarlet and red chromes. Examples of organic pigments are those from the azo, disazo, condensed azo, thioindigo, indanthrone, isoindanthrone, anthanthrone, anthraquinone, isodibenzanthrone, triphendioxazine, quinacridone and phthalocyanine series, especially copper phthalocyanine and its nuclear halogenated derivatives, and also lakes of acid, basic and mordant dyes. Carbon black, although strictly inorganic, behaves more like an organic pigment in its dispersing properties. Preferred organic pigments are phthalocyanines, especially copper phthalocyanines, monoazos, disazos, indanthrones, anthranthrones, quinacridones and carbon blacks.
Other preferred solids are: extenders and fillers such as talc, kaolin, silica, barytes and chalk; particulate ceramic materials such as alumina, silica, zirconia, titania, silicon nitride, boron nitride, silicon carbide, boron carbide, mixed silicon-aluminium nitrides and metal titanates; fire retardant fillers such as aluminium hydroxide and magnesium hydroxide; particulate magnetic materials such as the magnetic oxides of transition metals, especially iron and chromium, e.g. gamma-Fe2O3, Fe3O4, and cobalt-doped iron oxides, calcium oxide, ferrites, especially barium ferrites; and metal particles, especially metallic iron, nickel, cobalt and alloys thereof; and agrochemicals such as the fungicides flutriafen, carbendazim, chlorothalonil and mancozeb.
The liquid medium present in the dispersions of the invention is preferably a polar organic liquid or a substantially non-polar organic liquid or halogenated hydrocarbon. By the term xe2x80x9cpolarxe2x80x9d in relation to the organic medium is meant an organic liquid or resin capable of forming moderate to strong bonds as described in the article entitled xe2x80x9cA Three Dimensional Approach to Solubilityxe2x80x9d by Crowley et al in Journal of Paint Technology, Vol. 38, 1966, at page 269. Such organic media generally have a hydrogen bonding number of 5 or more as defined in the above mentioned article.
Examples of suitable polar organic liquids are amines, ethers, especially lower alkyl ethers, organic acids, esters, ketones, glycols, alcohols and amides. Numerous specific examples of such moderately strongly hydrogen bonding liquids are given in the book entitled xe2x80x9cCompatibility and Solubilityxe2x80x9d by Ibert Mellan (published in 1968 by Noyes Development Corporation) in Table 2.14 on pages 39-40 and these liquids all fall within the scope of the term polar organic liquid as used herein.
Preferred polar organic liquids are dialkyl ketones, alkyl esters of alkane carboxylic acids and alkanols, especially such liquids containing up to, and including, a total of 6 carbon atoms. As examples of the preferred and especially preferred liquids there may be mentioned dialkyl and cycloalkyl ketones, such as acetone, methyl ethyl ketone, diethyl ketone, di-isopropyl ketone, methyl isobutyl ketone, di-isobutyl ketone, methyl isoamyl ketone, methyl n-amyl ketone and cyclohexanone; alkyl esters such as methyl acetate, ethyl acetate, isopropyl acetate, butyl acetate, ethyl formate, methyl propionate, methoxy propylacetate and ethyl butyrate; glycols and glycol esters and ethers, such as ethylene glycol, 2-ethoxyethanol, 3-methoxypropylpropanol, 3-ethoxypropylpropanol, 2-butoxyethyl acetate, 3-methoxypropyl acetate, 3-ethoxypropyl. acetate and 2-ethoxyethyl acetate; alkanols such as methanol, ethanol, n-propanol, isopropanol, n-butanol and isobutanol and dialkyl and cyclic ethers such as diethyl ether and tetrahydrofuran.
The substantially non-polar, organic liquids which may be used, either alone or in admixture with the aforementioned polar solvents, are for example, aromatic hydrocarbons, such as toluene and xylene, aliphatic hydrocarbon such as pentane, heptane, octane and halogenated aliphatic and aromatic hydrocarbons, such as trichloroethylene, perchloroethylene and chlorobenzene. The non-polar organic liquid may also be a commercially available mixture such as an aliphatic or aromatic distillate, for example, white spirits.
The liquid medium may also be water or a mixture of water with a polar organic liquid, substantially non-polar organic liquid or halogenated hydrocarbon. When the liquid medium contains water, the amount of water is preferably less than 5% by weight of the liquid medium.
When the liquid medium is water it is preferred that the molecular weight of the polyester represented by "Brketopenst"(COxe2x80x94Axe2x80x94O)n(COxe2x80x94Bxe2x80x94O)m"Brketclosest" in formula 1 is less than or equal to the molecular weight of the polyether moiety represented by the group ROxe2x80x94.
Preferably, the liquid medium is a polar organic liquid.
Examples of suitable polar resins, as the medium for the dispersion form of the present invention, are film-forming resins such as are/suitable for the preparation of inks, paints and chips for use in various applications such as paints and inks. Examples of such resins include polyamides, such as Versamid(trademark) and Wolfamid(trademark), and cellulose ethers, such as ethyl cellulose and ethyl hydroxyethyl cellulose. Examples of paint resins include short oil alkyd/melamine-formaldehyde, polyester/melamine-formaldehyde, thermosetting acrylic/melamine-formaldehyde, long oil alkyd and multi-media resins such as acrylic and urea/aldehyde.
If desired, the dispersions may contain other ingredients, for example resins (where these do not already constitute the organic medium), binders, fluidising agents (such as those described in GB-A-1508576 and GB-A-2108143), anti-sedimentation agents, plasticisers, levelling agents and preservatives.
The dispersions typically contain from 5 to 95% by weight of the solid, the precise quantity depending on the nature of the solid and the quantity depending on the nature of the solid and the relative densities of the solid and the liquid medium. For example, a dispersion in which the solid is an organic material, such as an organic pigment, preferably contains from 15 to 60% by weight of the solid whereas a dispersion in which the solid is an inorganic material, such as an inorganic pigment, filler or extender, preferably contains from 40 to 90% by weight of the solid based on the total weight of dispersion.
The dispersion may be obtained by any of the conventional methods known for preparing dispersions. Thus, the solid, the liquid medium and the dispersant may be mixed in any order, the mixture then being subjected to a mechanical treatment to reduce the particles of the solid to an appropriate size, for example by ball milling, bead milling, gravel milling or plastic milling until the dispersion is formed. Alternatively, the solid may be treated to reduce its particle size independently or in admixture with either the liquid medium or the dispersant, the other ingredient or ingredients then being added and the mixture being agitated to provide the dispersion.
If the composition is required in dry form, the liquid medium is preferably volatile so that it may be readily removed from the particulate solid by a simple separation means such as evaporation. It is preferred, however, that the dispersion comprises the liquid medium.
If the dry composition consists essentially of the dispersant and the particulate solid, it preferably contains at least 0.2%, more preferably at least 0.5% and especially at least 1.0% dispersant based on weight of the particulate solid. Preferably the dry composition contains not greater than 100%, preferably not greater than 50%, more preferably not greater than 20% and especially not greater than 10% by weight based on the weight of the particulate solid.
As described hereinbefore, the dispersants of the invention are particularly suitable for preparing mill-bases where the particulate solid is milled in a liquid medium in the presence of both a particulate solid and a film-forming resin binder.
Thus, according to a still further aspect of the invention there is provided a mill-base comprising a particulate solid, dispersant, liquid medium and a film-forming resin.
Typically, the mill-base contains from 20 to 70% by weight particulate solid based on the total weight of the mill-base. Preferably, the particulate solid is not less than 30, and especially not less than 50% by weight of the mill-base.
The amount of resin in the mill-base can vary over wide limits but is preferably not less than 10%, and especially not less than 20% by weight of the continuous/liquid phase of the mill-base. Preferably, the amount of resin is not greater than 50% and especially not greater than 40% by weight of the continuous/liquid phase of the mill-base.
The amount of dispersant in the mill-base is dependent on the amount of particulate solid but is preferably from 0.5 to 5% by weight of the mill-base.
Dispersions and mill bases containing the dispersants of the invention are particularly suitable for use in paints, especially high solids paints, inks, especially flexographic, gravure and screen inks, and non-aqueous ceramic processes, especially tape-coating, doctor-blade, extrusion and injection moulding type processes.
The dispersants of the present invention exhibit advantage over known dispersants which contain a POAC chain derived from a single hydroxycarboxylic acid or lactone. In particular, they exhibit superior solubility in liquid media such as solvents and do not separate or crystallise when stored at 4xc2x0 C. for lengthy periods. When stored at low temperatures, separation can occur at xe2x88x92240xc2x0 C. but the dispersants readily re-dissolve on warming to 4-10xc2x0 C. When incorporated into paints and painting inks, the dispersants of the present invention give rise to higher gloss readings and lower haze values in the resultant paints and inks.
The invention is further illustrated by the following examples wherein all references to amounts are in parts by weight unless indicated to the contrary.